Caseless shaped charges for oilproducing boreholes



March 1, 1966 e. AUBERLINDER 3,237,559

CASELESS SHAPED CHARGES FOR OIL-PRODUCING BOREHOLES Filed Dec. 9, 1963Gerard Auer/nra er INVENTOR.

ATTORNEY United States Patent 3,237,559 CASELESS SHAPED CHARGES FOR OIL-PRODUCING BOREHOLES Gerard Auberlinder, Paris, France, assignor toSociete de Prospection Electrique Schlumberger S.A., Paris, France, acorporation of France Filed Dec. 9, 1963, Ser. No. 328,867 Claimspriority, application France, Dec. 14, 1962, 918,739 4 Claims. (Cl.102-24) This invention relates to shaped charges for use in completingoil wells, and more particularly, shaped charges for perforating thecasing of a well bore to place earth formations in fluid communicationwith the interior of the casing.

Shaped charges used heretofore, typically consist of an explosivecarried inside a pressure-resistant and fluid-impermeable capsule casemade of a material such as metal or glass. The explosive has a generallyconical recess which receives a thin metal liner. The capsule casetypically is a two piece construction with fluid-tight sealing meansbetween the two pieces, when assembled. Each of the above elementsforming the shaped charge, heretofore, has been considered essential forthe operation of a capsule-type shaped charge which is disposed in awell bore containing mud or other control fluids.

The pressure-resistant and fluid-tight capsule case has heretofore beenconsidered essential for three reasons: (1) it has attaching parts whichpermit the capsules to be connected to one another in an assembly; (2)since the explosive material is only compressed, the case providesmechanical protection; and (3) the casing protects the hydroscopicexplosive material against fluid disensitiling.

To detonate the explosive in the case, the thickness of the rear sectionof the casing is made sufliciently thin so that a detonating primer orblasting cord disposed in contact with the casing can be used todetonate the explosive in the case.

The sealing means fluid-tightly secured between the two case parts alsokeep the inside of the recess formed between the liner and case free offluids so that a volume of air under a reduced pressure is disposed infront of the liner providing a stand-01f space which improves theperformance of the charge when fired.

One of the major drawbacks of the above type of shaped charge is thatthe case is broken up upon firing forming considerable amounts of debriswhich is not easily removed from the well bore. The debris can alsoadversely affect subsequent completion operations and production fromthe well bore.

Furthermore, although the case provides confinement of the explosivepressures when the explosive material is detonated, it also reduces thevolume of explosive of a given charge. Hence, if the case can bereplaced with explosive material, the performance of the shaped chargecan be greatly improved.

The present invention relates to secondary explosives which arecompounded in a solid state with good mechanical properties andimperviousness to fluids. These secondary explosives also can be handledand subjected to considerable shock without detonating. An explosive ofthis type, for example, is Holtex which is described in French PatentNo. 1,146,818 and German Patent No. 1,147,159.

A hollow charge according to the invention is characterized by the factthat it is constituted essentially by a block of a secondary explosiveof a type appearing in a solid state, which is impervious to liquids,while a recess is provided to the front of the solid block and linermeans are provided for forming a shaped charge.

, of revolution 11.

Accordingly, it is an object of the present invention to provide a noveltype of shaped charge consisting only of a fluid-impervious,mechanically stable explosive without need of a container case.

According to a second object of the present invention, the recess in ashaped charge is provided with a liner incorporated in a fluid-tighthollow body with thin walls to resist pressure and provide alow-pressure stand-01f recess in front of the liner.

According to a third object of the present invention, a secondaryexplosive is provided with a rearward recess for a detonating primer.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with further objectsand advantages thereof, may best be understood by way of illustrationand example of certain embodiments when taken in conjunction with theaccompanying drawings in which:

FIGS. 1 and 2 illustrate in cross-section different embodiments of thepresent invention.

FIG. 1 illustrates an explosive block 10 made of a suitableiiuid-impervious secondary explosive which is formed as a shaped charge.Block 10 is formed by moulding the explosive under pressure and hassymmetry about an axis In the forward end of the block 10 is a conicalrecess 12 while the rearward end has a transverse slot 14 adapted toreceive a detonating or blasting cord (not shown). Inter-mediate thelength of the block 10 is an annular groove 16. Parallel, longitudinallyextending wire members 17 (shown in cross-section) can be received inthe groove to carry the charges into a well bore.

Block 10 has a liner adapted to be fitted within the conical recess 12.The liner includes a first inner copper cone 30 and a second outer cone32 (next to the explosive) made of zinc. The second outer cone is weldedalong its base at 33 to a hemispherically shaped metal cap 34 so as toform a fluid-tight hollow member. The thickness of the cap 34 and thetype of material used are selected so that the cap resists the pressuresencountered in the well bore. The interior 35 of the cap is, of course,at atmospheric pressure.

FIG. 2 illustrates another type of shaped charge. Block 20 similarly isprovided with a forward, tulip-shaped recess 2-2 and a rearward slot 24for the explosive blasting cord (not shown). Block 20 is also formedwith diametrically opposed male and female pin and socket attachingmeans 26 and 28 for connecting successive individual shaped charges toone another.

A hollow body 36 is adapted to engage the wall of the recess 22 in theshaped charge of FIG. 2. The material forming the liner 36, for example,may be glass or metal and can be formed to a thickness suitable forresisting the pressures it encountered in a well bore.

In addition to the advantages defined hereinabove, it may be stated thatthe fact of providing a direct contact between the secondary explosives10 and 2-2 and the detonating primers constituted by the blasting cordsallows resorting to blasting cords of a smaller diameter while ensuringreliably the firing of the shaped charge.

The liners illustrated in FIGS. 1 and 2 may be secured inside therecesses 12 and 22 through numerous means such as gluing, application ofcement, screwing, fitting with a force fit and the like.

The advantages of the liners according to the invention are obvioussince said liner may be made and separately inspected before assemblyand after inspection of the explosive block.

It is possible to imagine as a modification of the shaped chargesaccording to the invention, the application on the outer wall of theexplosive masses 10 and 20 of a thin coating or layer of a combustiblematerial. Such a coating or layer may be made, for instance, ofmagnesium or a combustible thermoplastic material so that no wastematerial is obtained when firing. It is possible to design the charge ina manner such that the projections 26 and 23 which allow forming ofstrings of shaped charges, may be made with the combustible material,which would allow producing more readily the explosive blocks whichwould then assume a shape of revolution.

The shapes of the explosive blocks, of the recesses, of the housingsprovided for the detonating primers, and of the securing means haveobviously been shown solely by way of example and they may be entirelydifferent from those disclosed without departing from the scope of thepresent invention. The same is obviously the case for the variousmethods of execution of the elements forming the shaped charge accordingto the invention.

As to the nature of the materials forming the liners in FIGS. 1 and 2,they may be quite different from those disclosed. It is possible, forinstance, to use in the case of FIG. 1 an outer coat 32-34 of a reactingmetal such as titanium or misch-metal with a suitable thickness and aninner cone 30 of copper.

On the other hand, although they are chiefly intended for a directlowering inside the borehole, it is obviously possible to house theshaped charges according to the invention in retrievable casing guns,which would allow positioning in chambers of a predetermined size,shaped charges the performances of which are clearly improved as aconsequence of the elimination of the metal casing used hitherto for themere mechanical protection of the explosive during the handling of thelatter.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. A shaped charge for perforating earth formations traversed by a wellbore having fluids therein and consisting of: a compressed body of afluid-imprevious secondary explosive uniformly disposed about a centralaxis and having integral extensions of said explosive projectinglaterally therefrom adapted for connection to a support and a generallyfrusto-conical recess in one end thereof diverging outwardly from thecentral axis of said compressed body, and a complementary, hollowedth=in-walled liner element received within said recess and adapted todevelop a perforating jet along said central axis.

2. The shaped charge of claim 1 wherein said liner element is composedof glass.

3. The shaped charge of claim 1 wherein said liner element is afluid-tight enclosed body extending beyond said one end of saidexplosive bore.

4. The shaped charge of claim 1 wherein said explosive body has a layerof combustible material coating the exterior surfaces.

References Cited by the Examiner UNITED STATES PATENTS 2,494,256 1/ 1950Muskat et al 10220 2,605,703 8/1952 Lawson. 2,749,990 6/ 1956 Carpenter102-20 3,016,014 1/1962 Lebourg. 3,117,518 1/1964 Porter.

FOREIGN PATENTS 980,903 1/1951 France.

1,146,818 5/1957 France.

SAMUEL FEINBERG, Primary Examiner.

BENJAMIN A. BORCHELT, Examiner.

1. A SHAPED CHARGE FOR PERFORATING EARTH FORMATIONS TRAVERSED BY A WELLBORE HAVING FLUIDS THEREIN AND CONSISTING OF: A COMPRESSED BODY OF AFLUID-IMPREVIOUS SECONDARY EXPLOSIVE UNIFORMLY DISPOSED ABOUT A CENTRALAXIS AND HAVING INTEGRAL EXTENSIONS OF SAID EXPLOSIVE PROJECTINGLATERALLY THEREFROM ADAPTED FOR CONNECTION TO A SUPPORT AND GENERALLYFRUSTO-CONCIAL RECESS IN ONE END THEREOF DIVERGING OUTWARDLY FROM THECENTRAL AXIS OF SAID COMPRESSED BODY, AND A COMPLEMENTARY, HOLLOWEDTHIN-WALLED LINER ELEMENT RECEIVED WITHIN SAID RECESS AND ADAPTED TODEVELOP A PERFORATING JET ALONG SAID CENTRAL AXIS.